The present invention pertains to secure end-to-end telecommunications and more particularly digital voice privacy in a cellular telecommunication system.
Currently commercial voice privacy is available over the public switched telephone network (PSTN).
Such commercially available voice privacy arrangements employ the use of analog scrambling of an analog baseband signal in the range of 300 to 3400 Hz. These commercially available voice privacy implementations use either frequency inversion or frequency modulation techniques. The quality level of the descrambled voice is poor at best and is dependent upon a number of parameters, such as telephone line quality, number of telecommunication transfers (hops) and number of exchanges to make the connection.
The cost of telephone elements is very important when providing service to highly populated relatively poor countries. Analog scramblers, as mentioned above, are used primarily because of the low cost to implement such technology. As a result, cost is a very important factor in the selection of telephone equipment in poorer countries.
In addition, scrambling technology may be regulated by the U.S. State Department and the National Institute of Standards (NIST) depending on the level of their complexity. As a result, this technology is more difficult to export by U.S. manufacturers to foreign countries as commercial products.
As a result, it would be desirable to have a low cost apparatus and method of scrambling which is digital in nature and provides upward compatibility to higher levels of security while maintaining a relatively high level of voice quality. In addition, it is desirable that the method of scrambling be simple enough so that only U.S. Department of Commerce approval will be required for export of the telephone components.